The Gorgon's Knot. Was: Re: Verio Peering Question

Sat Sep 29 02:30:19 UTC 2001

| > 	ip as-path access-list 1 permit _badguy_
| > 	
| > 	route-map fix-badguy permit 10
| > 	 descr proxy-aggregate the networks who are "holey"
| > 	 match as-path 1
| > 	
| > 	router bgp my-as
| > 	 aggregate-address bad.guy.blo.ck1 255.255.224.0 as-set suppress-map fix-badguy
| > 	 aggregate-address bad.guy.blo.ck2 255.255.224.0 as-set suppress-map fix-badguy
| > 	 ...
|
| And one aggregates a lone /24 with what? 

Oh yay, a bona fide techical question.  

The answer: 

	ACL 1 need not match only one AS

	as-set is there to deal with matches on multiple AS paths
		since we want to avoid looping announcements. conveniently,
		not only does it handle the case where ACL 1 matches
		lots of AS paths containing _X_, it can equally handle the
		case where ACL 1 matches lots of AS paths containing _Y_.

Next time I use the example I will remember to make ACL 1 longer,
and change "bad.guy.blo.ck1" (etc) into something along the lines
of "poo.rag.gre.g81", but perhaps more aesthetically pleasing.

	Sean.